Not sure if this is a bug or a feature request.
Synthetic silk does not work as a "fuel" source for the galacticraft grappling hook.

In case this is a bug i am going to post on GC github as well

Hi,

Yes it looks to be Galacticraft unfortunately, they check for the vanilla String item rather than using the Ore Dictionary. Hopefully it's an easy fix for them 😎

Thanks for the report!